Combination of Radiation and Immunotherapy Shows Promise in Melanoma

Combining radiation treatments with a new generation of immunotherapies is showing promise in the treatment of melanoma, according to a recent review.1

Cancer cells are killed by radiation through the damage it does to their DNA. A patient's immune system is harnessed to attack and kill cancer cells by immunotherapies. Combining the 2 therapies appears to have synergistic effects, according to this review by James S. Welsh, MD, and colleagues at Loyola Medicine and Loyola University Health System in Maywood, Illinois.

Melanoma is one of the most aggressive forms of skin cancer and it is responsible for the majority of deaths from skin cancer. When melanoma has reached stage 4, meaning the cancer has spread to other organs, 1-year survival rates are only 33% to 62%. The American Cancer Society reports melanoma will be diagnosed in an estimated 76 000 patients in the United States and approximately 10 000 people will die of the disease.

Spontaneous remission rarely occurs for patients with melanoma, but partial spontaneous regressions of melanoma lesions are more common. Although the cause of these effects is unknown, evidence suggests that the immune system is mounting an attack on cancer cells.

The abscopal effect supports the role of the immune system in melanoma. This is a rare phenomenon that happens when a localized treatment such as radiation shrinks the targeted tumor and stimulates the immune system to mount a systemic attack on cancer cells throughout the body.

A firsthand case of the abscopal effect was witnessed by Welsh when he administered radiation treatment to a patient whose melanoma had spread to his liver and bones. The radiation was intended merely to shrink a tumor in the patient's thigh bone, relieve pain, and reduce the risk of fracture. However, no trace of cancer was found anywhere in the patient on CT scan 3 months later.

Welsh and colleagues wrote that radiation is increasingly used alongside the new generation of checkpoint inhibitors and other immunotherapies, and the results are encouraging. However, they also wrote of the need to identify biomarkers that can predict which patients will respond to immunotherapy, as not all patients are able to mount an effective immune system response to fight melanoma.